1. Field of the Invention
The present invention relates to a data recording/reproduction device for recording and reproducing data of all types such as computer data and relates in particular to random access type data recording/reproduction devices. More specifically, the present invention relates to disk type data recording/reproduction devices utilized while mounted in a host device such as a computer system and relates in particular to disk type data recording/reproduction devices for recording and reproducing for recording and reproducing computer data requiring reliability, and video data and audio data requiring real-time characteristics.
2. Description of the Related Art
All types of information processing systems such as general-purpose computers contain a data recording/reproduction device to store large quantities of data and data for large scale applications in a non-volatile manner. Data recording/reproduction devices are for example comprised of disk type devices to store data on a rotating disk and tape type devices to store data on wound reel of tape.
A typical disk device is the HDD or hard disk drive. The hard disk drive has an amazing data storage capacity due to advances made in magnetic head technology and signal processing technology, etc. From 1990 up to the present for example, the surface recording density of data has increased approximately 60 percent each year. One 3.5 inch disk is expected to be capable of recording 10 to 20 gigabytes of data some time after the year 2000. In other words, one hard disk drive unit having a plurality of disks would have a recording capacity in excess of 100 gigabytes.
Therefore, by utilizing high efficiency digital moving picture compression technology such as DV (digital video) or MPEG2 (Moving Picture Experts Group Phase 2) made practical in recent years, moving picture information for a plurality of channels can be recorded on and reproduced from a hard disk drive, and multichannel video recorders capable of using a hard disk drive as a recording medium are now feasible.
However, from a historical point of view the hard disk drive was developed as an external storage device for computers and technical progress has been made in improving so-called discrete text type data and in making random access of data as fast as possible. In other words, hard disk drive operation is broken up or discrete along the time axis.
The computer system (hereafter xe2x80x9chostxe2x80x9d) incorporating the hard disk drive (HDD) issues commands (hereafter xe2x80x9chost commandsxe2x80x9d) specifying the recording or reproduction of data. The operations in response to each command from the host are executed one at a time as discrete operations. Restated, the hard disk drive guarantees high reliability but does not guarantee the recording or reproduction operation will finish within a specified time (real time guarantee).
One cause that prevents guaranteeing the actual time required for an operation is the retry process. The recording and reproduction of data on a hard disk drive is performed in short data sector unit (for example 512 bytes each) equivalent to the (information) packet used in communications technology. In the retry process, an operation is repeated again when an error occurs in implementing instructions such as to perform recording or reproduction of a data sector assigned by the host.
Various types of errors cause the retry operation to be used. On such error is in the operation (seek) to move the head to the target sector. To resolve the seek error, the recording and reproducing onto that target sector must be abandoned and continued elsewhere or retry operation must be performed. One retry requires from a few to several dozen milliseconds of wasted time and is a factor in poor real-time characteristics. Next, is retries (Writexe2x80x94Retry) during recording of data. If a deviation in the head position exceeding the established tolerance occurs such as from mechanical shock applied for example externally onto the hard disk drive during recording onto one data sector, then the recording operation will be halted. After waiting for the head to be restored to a normal position and the head to once again come to a position directly above the applicable sector by disk rotation, the recording of data onto the applicable sector starts once again (Writexe2x80x94Retry).
A third cause is retries (Readxe2x80x94Retry) during data reproduction (or playback). When an error is determined to occur that exceeds the correction capacity of the ECC (error correction code) in each sector during reproduction of one data sector, the operation stands by until the head once again comes to a position directly above the applicable sector by disk rotation and reproduction of the applicable sector starts again (Readxe2x80x94Retry). Further, when determined that the error was not corrected by one Readxe2x80x94Retry, a second Readxe2x80x94Retry is implemented. If the error is not a soft error due for example to noise, but is a hard error due definite cause such as damage of the magnetic film on the disk, then Readxe2x80x94Retry might be attempted 10 times or more without correctly reading the data, thus requiring at least 100 milliseconds of wasted time. Retries can therefore be a fatal problem in guaranteeing the actual time for a recording/reproduction operation.
The maximum number of retries implemented and other such error processing methods are fixedly incorporated into the design of related hard disk drives so that effective control according to the overall status of the disk recorder was not possible. Also, in the related art, a means was proposed for implementing or prohibiting retries without restrictions (For example, in a portion of the interfaces standards, of the ATA (AT-Attachment) established by ANSI (American National Standards Institute)) however a means for setting a maximum allowable time required for error processing, or a means for dynamic control according to the urgency or criticality (namely, the real-time characteristics) of recording and reproduction were not proposed.
In the disk type data recording/reproducing device of the related art, it was also assumed that data files would be handled discretely from each other so that instructions for recording or reproducing on individual sectors were treated as mutually unrelated items. So in applications such as multi-channel video and recorders with hard disk drives, even when recording/reproducing with a small number of long AV data streams, information on what data stream that the data for a recording/reproducing instruction belonged to was not utilized.
Therefore as related above, in the related art, the host device incorporating the disk type data recording/reproducing device had no simple means for monitoring items such as the error processing time of the disk device. Consequently, the related art had the problem that the continuous real time required during the recording or reproducing of information such as moving picture or audio information could not be guaranteed.
Still further, in the disk type data recording/reproducing device of the related art, the individual recording/reproducing operations were implemented without assigning a mutual rank or order (relation) so that a high throughput could not always be maintained.
In view of the above technical problems with the related art, the present invention therefore has the object of providing a disk type data recording/reproducing device ideal for processing suited for recording/reproducing of audio-visual data streams requiring real-time characteristics.
A further object of the present invention is to provide a disk type data recording/reproducing device ideal for maintaining the continuous real time characteristics for video recorders, and at the same time improve the average data rate and the number of audio-visual data streams capable of record/reproduction, and capable of high speed recording/reproducing of high quality audio-visual data.
In view of the above technical issues, according to one aspect of the present invention, the disk type data recording/reproducing device has a first operation mode for recording or reproduction of non-continuous information and, a second operating mode for recording or reproduction of continuous information.
A typical example of the continuous information referred to here is continuous image information compressed with the MPEG2 (Motion Picture Experts Group phase 2) method.
According to another aspect of the present invention, the disk type data recording/reproducing device has a first operation mode stressing reliability of data more than real time characteristics of recording and reproduction and, a second operation mode stressing real time characteristics more than the reliability of the data.
According to another aspect of the present invention, the disk type data recording/reproducing device comprises a disk as the recording medium, a record/reproduction section for recording and reproducing on the disk, and an error processing section for recovery from errors occurring during the recording or reproducing on the disk,
wherein the disk type data recording/reproducing device has a first operation mode with a maximum allowable error processing time more than a specified value in the error processing section and, a second operation mode with a maximum allowable error processing time less than a specified value in the error processing section.
The disk type data recording/reproducing device according to another aspect of the present invention is connected to a host system by way of a host interface, and besides recording and reproducing on the disk according to recording or reproducing commands received by way of the host interface, may be changed to the first operation mode or second operation mode according to a status change command received by way of the host interface.
The disk type data recording/reproducing device may also have means for actively performing an error processing procedure during the operation mode without being restricted by error processing time capacity, according to the urgency (criticality) for executing the recording or reproducing commands received by way the host interface.
The disk type data recording/reproducing device may also be capable of setting a large number of channels capable of simultaneous record or reproduction by using status change commands.
The disk type data recording/reproducing device according to another aspect of the present invention comprises a disk as a recording medium, a recording/reproducing section for performing record or reproduction on the disk, and an error processing section for restoring operation when an error occurs during recording or reproduction on the disk,
wherein during recording a maximum allowable error processing time can be set in the error processing section, and during reproduction a maximum allowable error processing time can be set in the error processing section.
The disk type data recording/reproducing device according to another aspect of the present invention is connected to a host system by way of a host interface, and besides recording and reproducing on the disk according to recording or reproducing commands received by way of the host interface, a maximum allowable error processing time can be set by the error processing section according to status change commands received by the host interface.
The disk type data recording/reproducing device contains means for actively changing the error processing procedure without being restricted by the maximum allowable error processing time, according to the urgency (criticality) for executing the recording or reproducing commands received by way of the host interface.
The disk type data recording/reproducing device may also be capable of setting a maximum number of channels capable of simultaneous record or reproduction by using status change commands.
The disk type data recording/reproducing device according to another aspect of the present invention comprises a disk as a recording medium, a recording/reproducing section for performing recording or reproducing on the disk, an error processing section for restoring operation when an error occurs during recording or reproduction on the disk, and a buffer memory for temporarily storing recording or reproduction data,
wherein the disk type data recording/reproducing device further comprises means for setting a maximum number of channels capable of simultaneous record or reproduction according to commands from the host and, means for changing internal data such as error processing procedures and areas assigned to the buffer memory, according to the maximum number of channels.
The disk type data recording/reproducing device according to another aspect of the present invention operates according to commands from a host system connected by way of a host interface and comprises a disk as a recording medium, a recording/reproducing section for performing recording or reproducing on the disk, and a buffer memory for temporarily storing recording or reproduction data,
wherein said disk type data recording/reproducing device further comprises stream identifiers in recording or reproduction commands received from the host showing the data stream that data for recording or reproduction belongs to, and
further comprises control means for adaptably controlling internal processing such as reference means for the buffer memory according to the stream identifiers.
The disk type data recording/reproducing device according to the various aspects of the present invention is utilized while connected to an external host system by way of a host interface in conformance with ATA (AT-Attachment) interface standards decided for instance by ANSI (American National Standards Institute) standards. One example of a host system is a digital image disk recorder for recording and reproducing data streams such as for video and audio data on the disk device of the present invention. The host system preferably utilizes a command set capable of being processed by the disk device in an operating mode limited by a specified error processing time.
The present invention was contrived based on the fact that the need for data reliability and for real time characteristics change according to the type of data handled by the HDD.
For instance, data reliability is indispensable in order for a hard disk drive (HDD) to handle computer data. Computer data containing errors is worthless for computer processing, and requires processing time and error correction.
In contrast, when a hard disk drive (HDD) handles audiovisual data, the recording and reproducing of data with real-time characteristics has the most importance and data reliability can be sacrificed to some extent. The reason being that even if the reproduced audio or video contains errors to some extent in the data, the limited range of human visual and audio perception allows those errors to be ignored or compensated. However if the real-time characteristics cannot be maintained, then the video or audio may intermittently cut off to an extent that cannot be ignored or compensated for, and the service quality will drastically deteriorate.
The disk type data recording/reproducing device (hereafter, simply referred to as xe2x80x9cdisk devicexe2x80x9d) of the present invention, besides having an operation mode for recording or reproduction of non-continuous information (in other words, discrete information), further has an operating mode for recording or reproduction of continuous information. The non-continuous information operation mode, hereafter referred to as IT (information technology) mode, is for handling data requiring high reliability such as computer data. The continuous information operation mode, hereafter referred to as AV (audio visual) mode, is for handling data requiring real time characteristics such as moving picture and audio data.
The disk device of the present invention can be connected by way of a host interface to a xe2x80x9chostxe2x80x9d such as a general-purpose computer or a digital motion picture recorder. This disk device further has a means to switch operation modes by way of the host interface, and has a means to set the allowable error processing time during recording or reproduction according to the mode switching. Therefore, in this disk device, the allowable error time can be actively set for IT (information technology) mode when highly reliable discrete information is required, or for AV (audio visual) mode for continuous information that requires real time characteristics.
The disk device also contains information indicating the urgency (criticality) in the individual recording or reproducing commands. The disk device also has an instruction means to assign information to individual data stream numbers and total channel numbers constituting a plurality of simultaneously recorded or reproduced data streams, and further has a means to change the operation inside the disk device based on this assigned information.
The disk device of the present invention in other words, possesses operation modes for recording and reproduction of moving picture data and audio data requiring real-time continuity, by means of limiting the error processing time. The host incorporating the disk device can therefore easily control the real-time continuity.
The host can implement even finer active control of the real-time continuity by specifying the urgency (criticality) in the individual record/reproduction instructions to the disk device.
The host can also inform the disk device of the required throughput by possessing a means to assign individual stream numbers and total channel numbers constituting a plurality of simultaneously recorded or reproduced data streams. The disk device is therefore capable of optimal internal processing such as data buffering.